I noticed that using osgShadow::ShadowMap in my scene makes everything very
dark, even nodes not part of the shadowed scene. Studying the OSG code, i
found this in ShadowMap.cpp, in ShadowMap::cull:
const_cast<osg::Light*>(selectLight)->setAmbient(osg::Vec4(0.0f,0.0f,0.0f,1.0f);
The light's ambient is set to black, and never restored! That certainly
explains why my whole scene is darker than normal.
I thought i might fix it by saving the ambient value, and restoring it later at
the bottom of ShadowMap::cull(). And in fact, this does restore the scene's
lighting - but, it prevents ShadowMap from drawing a shadow correctly.
Apparently, ShadowMap needs this black ambient set later after cull(), probably
during render(). But if the light is black during the scene's render(), that's
not good.
Does anyone see a solution to this? I can only imagine a couple of
possibilities:
1. Move the black-ambient from cull() to render pass somehow. I don't see any
explicit render() code in ShadowMap so i have no idea how this would work. It
seems like it must be possible.
2. Workaround: Make a second light, and set it with ShadowMap::setLight. Then
ShadowMap can use that light with black ambient, and leave the real light
alone. But, this is messy; we don't actually want 2 lights turned on in the
OpenGL pipeline, and we'd have to constantly copy values (like direction) from
the real light to the dummy light.
-Ben
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